module Merb::ConditionalGetMixin

Provides conditional get support in Merb core. Conditional get support is intentionally simple and does not do fancy stuff like making ETag value from Ruby objects for you.

The most interesting method for end user is request_fresh? that is used after setting of last modification time or ETag:

@example

def show
  self.etag = Digest::SHA1.hexdigest(calculate_cache_key(params))

  if request_fresh?
    self.status = 304
    return ''
  else
    @product = Product.get(params[:id])
    display @product
  end
end

Public Instance Methods

etag() click to toggle source

Value of the ETag header

@return [String] Value of ETag response header if set. @return [nil] If ETag header not set.

@api public

# File lib/merb-core/controller/mixins/conditional_get.rb, line 42
def etag
  headers[Merb::Const::ETAG]
end
etag=(tag) click to toggle source

Sets ETag response header by calling to_s on the argument

@param tag [#to_s] value of ETag header

@return [String] value of ETag header enclosed in double quotes as required by the RFC

@api public

# File lib/merb-core/controller/mixins/conditional_get.rb, line 32
def etag=(tag)
  headers[Merb::Const::ETAG] = %Q("#{tag}")
end
etag_matches?(tag = self.etag) click to toggle source

Test to see if the request's Etag matches the one supplied locally

@return [true] if ETag response header equals If-None-Match request header @return [true] if it does not.

@api public

# File lib/merb-core/controller/mixins/conditional_get.rb, line 52
def etag_matches?(tag = self.etag)
  tag == self.request.if_none_match
end
last_modified() click to toggle source

Value of the Last-Modified header

@return [Time] Value of Last-Modified response header if set. @return [nil] If Last-Modified not set.

@api public

# File lib/merb-core/controller/mixins/conditional_get.rb, line 75
def last_modified
  last_mod = headers[Merb::Const::LAST_MODIFIED]
  Time.rfc2822(last_mod) if last_mod
end
last_modified=(time) click to toggle source

Sets Last-Modified response header

@param time [Time,DateTime] The last modified time of the resource

@return [String] The last modified time of the resource in the format required by the RFC

@api public

# File lib/merb-core/controller/mixins/conditional_get.rb, line 63
def last_modified=(time)
  time = time.to_time if time.is_a?(DateTime)
  # time.utc.strftime("%a, %d %b %Y %X") if we could rely on locale being American
  headers[Merb::Const::LAST_MODIFIED] = time.httpdate
end
not_modified?(time = self.last_modified) click to toggle source

Test to see if the request's If-Modified-Since is satisfied

@param time [Time] Time to test if the If-Modified-Since header against

@return [true] Last-Modified response header is < than If-Modified-Since request header @return [false] otherwise

@api public

# File lib/merb-core/controller/mixins/conditional_get.rb, line 88
def not_modified?(time = self.last_modified)
  if !request.if_modified_since.nil? and !time.nil?
    time <= request.if_modified_since
  else
    false
  end
end
request_fresh?() click to toggle source

Tests freshness of response using all supplied validators

A response with no validators is always stale.

@return [true] ETag matches and entity is not modified @return [false] One or more validators failed, or none were supplied

@api public

# File lib/merb-core/controller/mixins/conditional_get.rb, line 104
def request_fresh?
  # make sure we have something to compare too.
  return false unless last_modified or etag

  fresh = true

  # only check if we have set the right headers
  fresh &&= etag_matches?(self.etag) if etag
  fresh &&= not_modified?(self.last_modified) if last_modified
  fresh
end